Units for Mmd from Mms

[martyh]

Trying to do a calculation of Mmd from Mms and I found a simple formula in This Thread my questions is about the units to use for mass and length. The formula given for air mass is

m = (8/3)*rho*r^3
where
rho = density of air
r = piston radius

My thought is piston radius in meters and density of air in kg per meter^3 .Using those units gets me 6.945 grams weight of air mass for a woofer with a piston radius of .128 meters (12” nominal woofer with sd=10.125) Does anybody know for sure what the units should be? If not, does the result seem reasonable?

Thanks,
Marty

 

[hollowboy]

I asked a similar thing, and got a good answer in this thread.

Thanks - Hollowboy - High Efficiency Speaker Asylum

Your units & maths look correct.

I got 14g airload for a 15"

 

[martyh]

Thanks for the quick answer hollowboy